This invention relates to regulated power supplies for use with deflection systems.
It is common practice to derive the ultor potential for a cathode ray tube, such as a television picture tube, by the rectification of horizontal retrace pulses obtained from the deflection system associated with the picture tube. It is recognized that an increase in ultor voltage can be caused by an increase in line voltage which energizes the television receiver or a decrease in picture tube beam current, the latter often being referred to as a decrease in beam loading. An excessive high voltage condition could cause arcing within the picture tube which could destroy the tube or components associated therewith or could generate harmful x-radiation from the tube. The direct current supplying the deflection system can be regulated to substantially overcome an increase in high voltage caused by variations of line voltage or beam current.
One type of regulator useful with deflecting systems is a switching regulator in which the duty cycle of a switch interposed between a source of current and the deflection system is controlled to effect regulation. A switching regulator may be transformer coupled to the deflection system with the transformer serving an isolation function allowing the regulator to be connected to the incoming power line whereas the deflection system can be isolated from the power line. Such a switching regulator is disclosed in copending U.S. application Ser. No. 607,512 filed Aug. 25, 1975 and entitled "Synchronized And Regulated Power Supply". That application discloses an arrangement in which an oscillator pulse is transformer coupled to the regulator to synchronize the operation of the power supply to the horizontal deflection rate to minimize the effects of switching, the transformer serving to isolate the oscillator from the power supply. The amplitude of the pulse is representative of variations of the deflection system direct current variations caused by power line variations. With this arrangement the number of connections between the isolated and non-isolated portions of the receiver is reduced. It would be desirable to further regulate such an arrangement against variations in high voltage caused by beam loading and still keep the number of connections between isolated and non-isolated chassis portions to a minimum.